Means of and apparatus for transmitting messages through submarine and other like cables



Jan. 2, 1934. w. ESTAUGH 1,942,278

MEANS OF AND APPARATUS FOR TRANSMITTING MESSAGES THROUGH SUBMARINE AND OTHER LIKE CABLES Filed Aug. 2, 1932 TV \R ATTORNEY Patented Jan. 2 1934 UNITED STATES MEANS OF AND APPARATUS FOR TRANS- MITTING MESSAGES THROUGH SUBMA- RINE AND OTHER LIKE CABLES William Estaugh,

Application August 2,

Wanstead, England 1932, Serial No. 627,266,

and in Great Britain August 14, 1931 7 Claims.

This invention relates to submarine and other like cables and has for its object improvements in the method of and apparatus for transmitting and receiving telegraphic and telephonic messages over a cable consisting of an insulated signalling conductor surrounded by an outer insulated conductor both of which are electrically charged at the receiving end by an earthed source so that the charge, which is mainly carried by the outer conductor, partly screens the inner conductor from earth capacity and enables messages to be transmitted through the inner conductor with little or no retardation or distortion.

According to a known method of signalling through such a cable the transmitting end of the inner conductor is connected through a signalling key to the terminal of the same sign of an earthed source of higher potential when signals are transmitted and the receiving instrument is connected between the receiving end of the said inner conductor and an earthed charging source. With this arrangement the two conductors are normally charged to the same potential at the receiving end but owing to resistance and leakage there is a gradual fall of potential towards the transmitting end of the outer conductor so that it does not so completely screen the inner conductor at that end, with the result that the earth will act inductively on the inner conductor where this potential drop occurs. With this arrangement the inner conductor is charged to a higher potential than the outer conductor when the signal key is operated, and is discharged through the receiver at the distant end when the signalling source at the transmitting end is disconnected from the said conductor.

According to another known method of signalling through a conductor of the type described above the transmitter is adapted to normally apply a predetermined higher potential to the inner conductor so as to produce a constant current at the receiving end when no messages are being sent and to increase'or decrease the potential of the said signalling current according to whether the signals transmitted are dots or dashes. For this purpose three batteries were employed at the transmitting end, one of which is adapted to apply the normal potential to the inner conductor and two smaller ones, each of which was of a strength equal to the increase and decrease of potential employed for signalling. These two smaller batteries were opposed to each other and either was adapted to be connected in series with the main battery by a suitable transmitting device.

In order to transmit and receive telephonic messages a telephonic transmitter and receiver were substituted for the telegraphic transmitter and receiver, while the normal potential conditions remained the same in both cases According to the present invention I apply a signalling current to the transmitting end of the inner conductor of such a potential that it never exceeds that of the charging current and is always higher than that on the outer conductor at the same end. With this arrangement the charge carried by the cable during signalling is not raised, as in the known methods referred to 7 above in which a signalling current of higher potential was applied at the transmitting end. By applying to the transmitting end of the inner conductor a potential that can be varied between that of the charging source and that of the trans mitting end of the outer conductor, a current of varying value is caused to pass through the receiving instrument without increasing the capacity oi the cable.

According to one mode of carrying out the present invention, the transmitter is adapted to normally apply a predetermined lower potential to the inner conductor so as to produce a constant current when no messages are being sent and to increase or decrease the potential of the said signalling currentsaccording to whether the signals are dots or dashesto such values that the augmented or decreased potential at the transmitting end shall be less than the potential of the charging source and greater than the pe tential of the outer conductor at the transmitting end respectively. I

For this purpose three batteries may be em-. ployed at the transmitting end, one of which is adapted to apply the normal potential to the inner conductor and two smaller ones, each of; which is of a strength equal to the increase or decrease of potential employed for signalling.

In order to transmit and receive telephonic messages a telephonic transmitter and receiver are substituted for the telegraphic transmitter and receiver, the normal potential conditions remain the same in both cases. I may, however, adopt any other known means of varyingthe potential applied to the line. i

I will now proceed to more particularly describe my invention with the aid of the accompanying drawing, in which Fig. 1 is a diagrammatic drawing showing the improved arrangement of cable with transmitting,- receiving and amplifying apparatus, according to one mode of carrying'out the present invention,

Fig. 2 is a cross-section through the cable employed,

Fig. 3 is a diagram showing an alternative ance.

proximation of the normal potential conditions of the respective conductors at both ends.

According to the arrangement shown in Figure 1, a is an insulated inner signalling conductor and b, is an insulated outer conductor which is concentrically disposed around it. The inner conductor a, and the outer conductor 1), are connected through a potentiometer g to the positive terminal of the battery 1 which has its negative terminal connected to the earthed return conductor e at the receiving end B. The potentiometer g is connected across the battery f to enable the potential applied to be adjusted.

With this arrangement the outer conductor 19 and the inner conductor a will both be constantly charged but the inner conductor a, will be electrically screened from the inductive ef fect of the return conductor e by this said conductor b. This screening however, is not so effe ctual at the transmitting end owing to the fall in potential that will occur along the outer conductor b, due to current leakage and its resist- The result of this will be that the inner conductor a, will carry a certain portion of the total charge in the cable, and the value of the charge carried by the signalling conductor a, will be proportional to the difference in potential that exists between the respective conductors a and b and their respective capacities with relation to the return conductor e.

' At the sending station T the negative pole of the battery 7' is also connected to the earthed return conductor e and its positive pole is connected to the inner conductor a through potentiometer m and also potentiometer n which controls the signal potential.

Potentiometer m is adjusted to normally apply a predetermined lower potential to the signalling V conductor a so as to permit a constant current to pass from the charging battery ,1 through the ignalling conductor a, and the primary circuit of thereceiving transformer s at the receiving end. The electrostatic voltmeter o is for the purpose of measuring this normal signal poten-' tial which must not be lower than that of the outer conductor b, at the same end. Therefore, in order to obtain a suitable potential drop at the sending end of the outer conductor 1), it may if necessary be earthed through a'suitable resistance.

For the purpose of transmitting signals two batteries is and Z of approximately equal value may be employed. Potentiometer n is adjusted to the desired value for signalling which may be measured on voltmeter 0.

To transmit a signal the section of the resistance of the potentiometer n across which the potential of either of the batteries is or Z is conducted, is interposed between the battery 7' and the conductor a by the closure of the transmitting key p. When the battery is is thus interposed a corresponding rise in thecurrent in the primary circuit of the transformer 3 takes place and induces a corresponding current rise in its secondary circuit which may indicate a dot or dash as the case may be. In like manner, when the transmitting key 10 interposes the opposed battery Z a corresponding reduction takes place in the current through the inner conductor a and the transformer 8. According to the arragement shown, a thermionic valve is employed to detect and amplify the received signals in which one end of the secondary circuit of the transformer s is connected to the grid 3 of a thermionic valve 1, the filament 2 of which is heated by the battery 4. The plate 5 of the valve is connected to one terminal of the receiver t whose other terminal is connected to the positive pole of the high tension battery 6, and the negative pole of the latter is connected to one side of the filament battery 4.

The adjustable resistance indicated at r, at the receiving end is to compensate for the impedance of the primary circuit of the receiving transformer s, and also for adjusting the sending potential between the outer conductor 12, and the earthed return conductor e, in order that best screening conditions may be obtained during the transmission of signals. To assist in making these adjustments, a galvanometer or other suitable detecting device q is included in the connection between the outer conductor 1), and the posi' tive pole of the battery f. When signals are being transmitted through the inner conductor a the resistance indicated at r is adjusted until no defiection is obtained on the detecting device q. This will then indicate that the charge on the outer conductor 27, remains constant during transmission of signals and that the signal charge is confined solely to the signalling conductor (1.

According to the arrangement shown in Figure 3, a suitable transformer is also employed at the transmitting end. One end of the secondary circuit of the transformer u is connected pole of the battery Z, while the opposite extremity of the said primary coil is connected to the transmitting key 11. A signal is transmitted by closing the primary circuit with one of the batteries k or Z, which will cause a current to be induced in the secondary circuit of the transformer u, the signalling conductor a, and the primary circuit of the receiving transformer s. The current. induced in the secondary circuit of the transformer s is detected and amplified as already described.

I may employ any other known means of applying a varying signal potential to the line without departing from the spirit of the present invention.

In applying the present invention for the transmission and reception of telephonic signals the normal potential conditions remain the same but instead of the telegraphic transmitter and batteries and the telegraphic receiver described in connection with Figures 1 to 3 a telephonic transmitter 1) is connected in series with the battery w and the primary circuit of the transformer a, which has one end of its secondary circuit connected to the signalling conductor a, while its opposite extremity is connected to the positive pole of the battery 9', as shown in Figure 4'. At the receiving end a telephonic receiver 29, may be inserted in the place of the telegraphic receiver.

In order to transmit telephonic signals the lpotentiometer m,'is adjusted to normally apply a predetermined. lower potential to the signalling conductor a so as to produce a constant current from the receiving end through the primary circuit of the transformer s, the signalling conductor P One terminal of a telephone receiver t is connected to the plate 5 of the valve 1' and the other terminal is connected to the positive pole of the high tension battery 6, the negative pole of which is connected to one side of the filament battery Z.

The transmitter 12, may be of any known kind either of the magneto or resistance varying type.

Sound waves acting on the diaphragm of the microphone 11, will cause variations to occur in the current flowing in the primary circuit of the transformer it, which will cause to be induced in its secondary circuit, similar current variations.

These current variations in passing through the signalling conductor a and the primary circuit of the transformer s will cause to be induced in its secondary circuit impulses which will represent the amount of increase or decrease in the normal current of the battery 7' at the transmitting end.

These impulses will be detected by the grid 3, of the thermionic valve 1, and amplified in the plate circuit of the same in the usual known manner. I may employ any number of amplifying valve stages of known design to give the desired signal magnification.

In some cases different telephonic currents may be impressed in any known manner upon separate oscillating circuits of different periodicity, that directly or indirectly through one or more transformers apply their modulated currents to the inner conductor at the transmitting end of the cable, and. the various sets of signals may be detected and amplified in any known manner at the receiving station in tuned circuits which may be connected to different land lines. In this way a plurality of signals may be transmitted simultaneously over the same cable.

Reference to the diagrammatic chart shown at Figure 5, will give a general idea of the normal potential conditions of the respective conductors. At the receiving end R, conductors a and b are both charged to potential V, by the battery while at the transmitting end T, the battery 1' of a somewhat lower potential V is connected to the inner conductor a, and the lower potential of the outer conductor 2), at this end is represented at V When telegraphic or telephonic signals are being transmitted the potential of V must not be varied above that of V or below that of V this applies to all the foregoing arrangements shown in Figures 1 to 4.

I may employ any known method of superimposing telephonic currents on the signalling conductor, and in some cases I may employ an insulated return conductor without departing from the spirit of the invention.

I claim:

1. Means and apparatus for transmitting messages through a submarine or other like cable consisting of an inner insulated conductor; an outer insulated conductor; an earthed electrical charging source at the receiving end connected to said inner and outer conductors. whereby said outer conductor screens said inner conductor from earth capacity except towards the transmitting end of the cable where the potential of said outer conductor progressively falls owing to leakage and resistance; an earthed electrical signalling source Whose like terminal is connected to the transmitting end of the inner conductor and signaling means for varying the potential of said signalling source between the potentials applied by the charging source to said inner and outer conductors at the transmitting end so as to cause signalling currents of varying strength to pass from the receiving end through signal receiving instruments, to the transmitting end of the cable substantially as set forth.

2. Means and apparatus for transmitting messages through a submarine or other like cable according to claim 1 in which the signalling source at the transmitting end comprises an earthed main battery connected in series with the inner conductor through two opposed smaller batteries of equal strength each of which is provided with a shunt across its terminals controlled by a. signal key by means of which either can be short circuited so as to vary the potential opposed to the charging source at the receiving end within the defined limits substantially as set forth.

3. Means and apparatus for transmitting messages through a submarine or other like cable according to claim 1 in which the signalling sourcecomprises an earthed main battery connected in series with the inner conductor through two resistances, and two opposed smaller batteries of equal strength each of which is respectively connected in parallel with one of said resistances through a signalling key by means of which the potential applied to the inner conductor can be augmented or reduced within the defined limits substantially as set forth.

4. Means and apparatus for transmitting messages through a submarine or other like cable according to claim 1 in which the signalling source comprises an earthed main battery connected in series with the inner conductor through the secondary circuit of a transformer and a telephonic transmitter connected in series with the primary circuit of said transformer so that the potential applied to the inner conductor can be augmented or reduced by the telephonic impulse superimposed thereon within the defined limits substantially as set forth.

5. Means and apparatus for transmitting messages through a submarine or other like cable according to claim 1 in which the variations in potential are detected at the receiving end'by a thermionic valve connected to the secondary circuit of a transformer Whose primary circuit is connected between the inner conductor and the charging source, substantially as set forth.

6. Means and apparatus for transmitting messages through a submarine or other like cable according to claim 1 in which an oscillating circuit adapted to have telephonic currents impressed on it is connected to the primary circuit of a transformer and an earthed electrical signalling source in series with the secondary circuit of said transformer and the inner conductor so that the potential applied to said inner conductor is augmented or reduced within the defined limits by the telephonic impulses impressed upon a carrier wave, substantially as set forth.

7. Means and apparatus for transmitting messages through a submarine or other like cable according to claim 1 in which a plurality of oscillating circuits having different periods and adapted to have different telephonic currents impressed on each are operatively associated with the primary circuit of a transformer; an earthed electrical signalling source in series with the secondary circuit of said transformer and the inner conductor so that the potential applied to said inner conductor is augmented or reduced within the defined limits by the carrier waves having the telephonic impulses impressed upon them; and a plurality of tuned receivers at the receiving end of said cable substantially as set forth. WILLIAM ESTAUGH. 

